some people can be so funny, is it a must to accept to help someone? Even though you sounded a bit harsh but you made your points clear to her earlier on, she shouldn't have brought the baby.
If she really needs someone to help her with the baby then I think it would be nice for her to get someone to babysit her child.
I know how such things feels, I know you felt bad for reacting that way. Well, it's life. Sorry about the experience.